Cut-off points defining normal and asthmatic bronchial reactivity to exercise and inhalation challenges in children and young adults

A proposal to account for the stimulus, the mechanism, and the mediators released in exercise-induced bronchoconstriction

Exercise induced bronchoconstriction (EIB) describes the transient narrowing of the airways that follows vigorous exercise. It commonly occurs in children and adults who have asthma and in elite athletes. The primary stimulus is proposed to be loss of water, by evaporation, from the airway surface due to conditioning inspired air. The mechanism, whereby this evaporative loss of water provokes contraction of the bronchial smooth muscle, is thought to be an increase in osmolarity of the airway surface liquid. The increase in osmolarity causes mast cells to release histamines, prostaglandins, and leukotrienes. It is these mediators that contract smooth muscle causing the airways to narrow.

An Overview on the Primary Factors That Contribute to Non-Allergic Asthma in Children

The prevalence of non-allergic asthma in childhood is low, peaking in late adulthood. It is triggered by factors other than allergens, like cold and dry air, respiratory infections, hormonal changes, smoke and air pollution. In the literature, there are few studies that describe non-allergic asthma in pediatric age. Even though it is a less common disorder in kids, it is crucial to identify the causes in order to keep asthma under control, particularly in patients not responding to conventional treatments. In this review, we discuss non-IgE-mediated forms of asthma, collecting the latest research on etiopathogenesis and treatment.

Can the response to a single dose of beclomethasone dipropionate predict the outcome of long-term treatment in childhood exercise-induced bronchoconstriction?

BACKGROUND

Exercise-induced bronchoconstriction (EIB) is a frequent and highly specific symptom of childhood asthma. Inhaled corticosteroids (ICS) are the mainstay of controller therapy for EIB and asthma; however, a proportion of asthmatic children and adolescents is less responsive to ICS. We hypothesized that a single dose response to ICS could function as a predictor for individual long-term efficacy of ICS.

OBJECTIVE

To assess the predictive value of the bronchoprotective effect of a single-dose beclomethasone dipropionate (BDP) against EIB for the bronchoprotective effect of 4 weeks of treatment, using an exercise challenge test (ECT).

METHODS

Thirty-two steroid-naïve children and adolescents aged 6 to 18 years with EIB were included in this prospective cohort study. They performed an ECT at baseline, after a single-dose BDP (200µg) and after 4 weeks of BDP treatment (100 µg twice daily) to assess EIB severity.

RESULTS

The response to a single-dose BDP on exercise-induced fall in FEV1 showed a significant correlation with the response on exercise-induced fall in FEV1 after 4 weeks of BDP treatment (r = .38, p = .004). A reduction in post-exercise fall in FEV1 of more than 8% after a single-dose BDP could predict BDP efficacy against EIB after 4 weeks of treatment with a positive predictive value of 100% (CI: 86.1-100%) and a negative predictive value of 29.4% (CI: 11.7%-53.7%).

CONCLUSION

We found that the individual response to a single-dose BDP against EIB has a predictive value for the efficacy of long-term treatment with BDP. This could support clinicians in providing personalized management of EIB in childhood asthma.

Cut-off value for exercise-induced bronchoconstriction based on the features of the airway obstruction

The current cut-off value for diagnosing exercise-induced bronchoconstriction (EIB) in adults—percent fall in FEV₁ (ΔFEV₁) ≥ 10% after exercise challenge test (ECT)—has low specificity and weak evidences. Therefore, this study aimed to identify the cut-off value for EIB that provides the highest diagnostic sensitivity and specificity. Participants who underwent the ECT between 2007 and 2018 were categorized according to ΔFEV₁: definite EIB (ΔFEV₁ ≥ 15%), borderline (10% ≤ ΔFEV₁ < 15%), and normal (ΔFEV₁ < 10%). Distinct characteristics of the definite EIB group were identified and explored in the borderline EIB group. A receiver operating characteristic curve was plotted to determine the optimal cut-off value. Of 128 patients, 60 were grouped as the definite EIB group, 23 as the borderline group, and 45 as the normal group. All participants were men, with a median age of 20 years (interquartile range [IQR:] 19–23 years). The definite EIB group exhibited wheezing on auscultation (P < 0.001), ΔFEV₁/FVC ≥ 10% (P < 0.001), and ΔFEF_25–75% ≥ 25% (P < 0.001) compared to other groups. Eight (8/23, 34.8%) patients in the borderline group had at least one of these features, but the trend was more similar to that of the normal group than the definite EIB group. A cut-off value of ΔFEV₁ ≥ 13.5% had a sensitivity of 98.5% and specificity of 93.5% for EIB. Wheezing on auscultation, ΔFEV₁/FVC ≥ 10%, and ΔFEF_25–75% ≥ 25% after ECT may be useful for the diagnosis of EIB, particularly in individuals with a ΔFEV₁ of 10–15%. For EIB, a higher cut-off value, possibly ΔFEV₁ ≥ 13.5%, should be considered as the diagnostic criterion.

Self-reported exercise-induced dyspnea and airways obstruction assessed by oscillometry and spirometry in adolescents

BACKGROUND

Self-reported exercise-induced dyspnea (EID) is common among adolescents. Possible underlying pathologies are exercise-induced bronchoconstriction (EIB) and laryngeal obstruction (EILO). The forced oscillation technique (FOT) may evaluate exercise-induced changes in airway caliber.

AIM

To investigate in adolescents the relationship between EID, EIB (post-exercise fall in forced expiratory volume in 1s (FEV₁ )≥10%), EILO, and post-exercise challenge changes in FOT parameters.

METHODS

One hundred and forty-three subjects (97 with EID) of 13-15 years old underwent a standardized exercise challenge with FOT measurement and spirometry repeatedly performed between 2 and 30 min post-exercise. EILO was studied in a subset of 123 adolescents. Subjects showing greater changes than the healthy subgroup in the modulus of the inspiratory impedance were considered FOT responders.

RESULTS

EID-nonEIB subjects presented similar post-exercise changes in all FOT parameters to nonEID-nonEIB adolescents. Changes in all FOT parameters correlated with FEV₁ fall. 45 of 97 EID subjects responded neither by FEV₁ nor FOT to exercise. 19 and 18 subjects responded only by FEV₁ (onlyFEV₁ responders) or FOT (onlyFOTresponders), respectively. Only a lower baseline forced vital capacity (FVC)%predicted and a higher FEV₁ /FVC distinguished the onlyFEV₁ responders from onlyFOTresponders. FOT parameters did not present specific post-exercise patterns in EILO subjects.

CONCLUSION

FOT can be used to identify post-exercise changes in lower airway function. However, EID has a modest relation with both FEV₁ and FOT responses, highlighting the need for objective testing. More research is needed to understand whether onlyFEV₁ responders and onlyFOTresponders represent different endotypes.

Volatile organic breath components and exercise induced bronchoconstriction in asthmatic children

INTRODUCTION

Asthma is one of the most common chronic diseases in childhood and is generally characterized by exercise induced bronchoconstriction (EIB). Assessing EIB is time consuming and expensive as it requires a fully equipped pulmonary function laboratory. Analysis of volatile organic compounds (VOCs) in breath is a novel technique for examining biomarkers which may associate with asthma features. The aim of this pilot study was to identify potential markers in the relationship between EIB and VOCs.

METHODS

Children between four and 14 years old were asked to provide a breath sample prior to undergoing an exercise challenge test to assess for EIB.

RESULTS

Breath samples were collected and analyzed in 46 asthmatic children, 21 with EIB and 25 without EIB (NO-EIB). Molecular features (MFs) were not significantly different between EIB and NO-EIB controls. 29 of the 46 children were corticosteroid naïve, 10 with EIB and 13 without. In the corticosteroid naïve group EIB was associated with increased MF23 and MF14 in the lower breath sample (p-value < 0.05).

CONCLUSION

This pilot study shows that EIB was related to an increased MF14 and MF23 in corticosteroid naïve children. The tentative identities of these compounds are octanal and dodecane/tetradecane respectively. These candidate biomarkers have a potential to enable non-invasive diagnosis of EIB in steroid-naïve children. Trial registration This study is registered in the Netherlands trial register (trial no. NL6087) at 14 February 2017.

Does exercise-induced bronchoconstriction affect physical activity patterns in asthmatic children?

Exercise-induced bronchoconstriction (EIB) is a sign of uncontrolled childhood asthma and classically occurs after exercise. Recent research shows that EIB frequently starts during exercise, called breakthrough-EIB (BT-EIB). It is unknown whether this more severe type of EIB forces children to adapt their physical activity (PA) pattern in daily life. Therefore, this pilot study aims to investigate daily life PA (amount, intensity, duration, and distribution) in children with BT-EIB, 'classic' EIB, and without EIB. A Fitbit Zip activity tracker was used for one week to objectively measure daily life PA at one-minute intervals. Thirty asthmatic children participated. Children with BT-EIB were less physically active compared to children without EIB (respectively 7994 and 11,444 steps/day, p = .02). Children with BT-EIB showed less moderate-to-vigorous PA compared to the children without (respectively 117 and 170 minutes/day, p = .02). Children with EIB (both BT and classic) had significant shorter bouts of activity and a less stretched distribution of bout lengths compared to the non-EIB group (all p < .05). These results emphasize a marked association between EIB severity and PA patterns in daily life, stressing the need for a thorough clinical evaluation of exercise-induced symptoms in childhood asthma.

Predictors and reproducibility of exercise-induced bronchoconstriction in cold air

Background

Physical activity is an important part of life, and hence exercise-induced bronchoconstriction (EIB) can reduce the quality of life. A standardized test is needed to diagnose EIB. The American Thoracic Society (ATS) guidelines recommend an exercise challenge in combination with dry air. We investigated the feasibility of a new, ATS guidelines conform exercise challenge in a cold chamber (ECC) to detect EIB. The aim of this study was to investigate the surrogate marker reaction to methacholine, ECC and exercise challenge in ambient temperature for the prediction of a positive reaction and to re-evaluate the reproducibility of the response to an ECC.

Methods

Seventy-eight subjects aged 6 to 40 years with suspected EIB were recruited for the study. The subjects performed one methacholine challenge, two ECCs, and one exercise challenge at an ambient temperature. To define the sensitivity and specificity of the predictor, a receiver-operating characteristic curve was plotted. The repeatability was evaluated using the method described by Bland and Altman (95% Limits of agreement).

Results

The following cut-off values showed the best combination of sensitivity and specificity: the provocation dose causing a 20% decrease in the forced expiratory volume in 1 s (PD₂₀FEV₁) of methacholine: 1.36 mg (AUC 0.69, p < 0.05), the maximal decrease in FEV₁ during the ECC: 8.5% (AUC 0.78, p < 0.001) and exercise challenges at ambient temperatures: FEV₁ 5.2% (AUC 0.64, p = 0.13). The median decline in FEV₁ was 14.5% (0.0–64.2) during the first ECC and 10.7% (0.0–52.5) during the second ECC. In the comparison of both ECCs, the Spearman rank correlation of the FEV₁ decrease was r = 0.58 (p < 0.001). The 95% limits of agreement (95% LOAs) for the FEV₁ decrease were − 17.7 to 26.4%.

Conclusions

The surrogate markers PD₂₀FEV₁ of methacholine and maximal decrease in FEV₁ during ECC can predict a positive reaction in another ECC, whereas the maximal FEV₁ decrease in an exercise challenge at an ambient temperature was not predictive. Compared with previous studies, we can achieve a similar reproducibility with an ECC.

Clinical trial registration

NCT02026492 (retrospectively registered 03/Jan/2014).

Exercise-induced bronchoconstriction: prevalence, pathophysiology, patient impact, diagnosis and management

Exercise-induced bronchoconstriction (EIB) can occur in individuals with and without asthma, and is prevalent among athletes of all levels. In patients with asthma, symptoms of EIB significantly increase the proportion reporting feelings of fearfulness, frustration, isolation, depression and embarrassment compared with those without symptoms. EIB can also prevent patients with asthma from participating in exercise and negatively impact their quality of life. Diagnosis of EIB is based on symptoms and spirometry or bronchial provocation tests; owing to low awareness of EIB and lack of simple, standardised diagnostic methods, under-diagnosis and mis-diagnosis of EIB are common. To improve the rates of diagnosis of EIB in primary care, validated and widely accepted symptom-based questionnaires are needed that can accurately replicate the current diagnostic standards (forced expiratory volume in 1 s reductions observed following exercise or bronchoprovocation challenge) in patients with and without asthma. In patients without asthma, EIB can be managed by various non-pharmacological methods and the use of pre-exercise short-acting β2-agonists (SABAs). In patients with asthma, EIB is often associated with poor asthma control but can also occur in individuals who have good control when not exercising. Inhaled corticosteroids are recommended when asthma control is suboptimal; however, pre-exercise SABAs are also widely used and are recommended as the first-line therapy. This review describes the burden, key features, diagnosis and current treatment approaches for EIB in patients with and without asthma and serves as a call to action for family physicians to be aware of EIB and consider it as a potential diagnosis.

[Guidelines for methacholine provocation testing]

Bronchial challenge with the direct bronchoconstrictor agent methacholine is commonly used for the diagnosis of asthma. The "Lung Function" thematic group of the French Pulmonology Society (SPLF) elaborated a series of guidelines for the performance and the interpretation of methacholine challenge testing, based on French clinical guideline methodology. Specifically, guidelines are provided with regard to the choice of judgment criteria, the management of deep inspirations, and the role of methacholine bronchial challenge in the care of asthma, exercise-induced asthma, and professional asthma.

Global prevalence of exercise-induced bronchoconstriction in childhood: A meta-analysis

AIM

This systematic review and meta-analysis aimed to estimate the global prevalence of exercise-induced bronchoconstriction (EIB) in children and adolescents.

METHOD

We searched PubMed, Google Scholar, and the Virtual Health Library-BIREME from inception to December 23, 2017. We selected observational studies that reported the prevalence of EIB (diagnosed by exercise challenge test) in children and adolescents aged 5-18 years. We conducted random-effects meta-analyses to estimate the pooled prevalence of EIB and 95% CI.

RESULTS

We included 66 studies (55 696 participants, 5670 cases of EIB) in the review, of which 33 in general population of children and adolescents, 10 in child and adolescent athletes and 23 in children and adolescents with asthma. The global mean prevalence of EIB in the general population of children and adolescents was 9% (IC95%: 8-10%), with a higher rate (12%) in Asia-Pacific and America. The mean prevalence of EIB was 15% (95% CI: 9-21%) in child and adolescent athletes, and 46% (95% CI: 39-53%) in children and adolescents with asthma. We estimated that, globally, around 16.5 million (95% CI: 15-18 million) children and adolescents up to 18 years of age may have EIB.

CONCLUSION

EIB in childhood should be considered as a global public health problem that needs more attention. The substantial heterogeneity between studies highlights the need for evidence-based guidelines for diagnosis of EIB in this age group.

BMI predicts exercise induced bronchoconstriction in asthmatic boys

BACKGROUND

Exercise induced bronchoconstriction (EIB) is a frustrating morbidity of asthma in children. Obesity has been associated with asthma and with more severe EIB in asthmatic children.

OBJECTIVES

To quantify the effect of BMI on the risk of the occurrence of EIB in children with asthma.

METHODS

Data were collected from six studies in which exercise challenge tests were performed according to international guidelines. We included 212 Children aged 7-18 years, with a pediatrician-diagnosed mild-to-moderate asthma.

RESULTS

A total of 103 of 212 children (49%) had a positive exercise challenge (fall of FEV₁  ≥ 13%). The severity of EIB, as measured by the maximum fall in FEV₁ , was significantly greater in overweight and obese children compared to normal weight children (respectively 23.9% vs 17.9%; P = 0.045). Asthmatic children with a BMI z-score around +1 had a 2.9-fold higher risk of the prevalence of EIB compared to children with a BMI z-score around the mean (OR 2.9; 95%CI: 1.3-6.1; P < 0.01). An increase in BMI z-score of 0.1 in boys led to a 1.4-fold increased risk of EIB (OR 1.4; 95%CI: 1.0-1.9; P = 0.03). A reduction in pre-exercise FEV₁ was associated with a higher risk of EIB (last quartile six times higher risk compared to highest quartile (OR 6.1 [95%CI 2.5-14.5]).

CONCLUSIONS

The severity of EIB is significantly greater in children with overweight and obesity compared to non-overweight asthmatic children. Furthermore, this study shows that the BMI-z-score, even with a normal weight, is strongly associated with the incidence of EIB in asthmatic boys.

Exercise-induced bronchoconstriction update-2016

The first practice parameter on exercise-induced bronchoconstriction (EIB) was published in 2010. This updated practice parameter was prepared 5 years later. In the ensuing years, there has been increased understanding of the pathogenesis of EIB and improved diagnosis of this disorder by using objective testing. At the time of this publication, observations included the following: dry powder mannitol for inhalation as a bronchial provocation test is FDA approved however not currently available in the United States; if baseline pulmonary function test results are normal to near normal (before and after bronchodilator) in a person with suspected EIB, then further testing should be performed by using standardized exercise challenge or eucapnic voluntary hyperpnea (EVH); and the efficacy of nonpharmaceutical interventions (omega-3 fatty acids) has been challenged. The workgroup preparing this practice parameter updated contemporary practice guidelines based on a current systematic literature review. The group obtained supplementary literature and consensus expert opinions when the published literature was insufficient. A search of the medical literature on PubMed was conducted, and search terms included pathogenesis, diagnosis, differential diagnosis, and therapy (both pharmaceutical and nonpharmaceutical) of exercise-induced bronchoconstriction or exercise-induced asthma (which is no longer a preferred term); asthma; and exercise and asthma. References assessed as relevant to the topic were evaluated to search for additional relevant references. Published clinical studies were appraised by category of evidence and used to document the strength of the recommendation. The parameter was then evaluated by Joint Task Force reviewers and then by reviewers assigned by the parent organizations, as well as the general membership. Based on this process, the parameter can be characterized as an evidence- and consensus-based document.

Vigorous Exercise Can Cause Abnormal Pulmonary Function in Healthy Adolescents

RATIONALE

Although exercise-induced bronchoconstriction is more common in adolescents with asthma, it also manifests in healthy individuals without asthma. The steady-state exercise protocol is widely used and recommended by the American Thoracic Society (ATS) as a method to diagnose exercise-induced bronchoconstriction. Airway narrowing in response to exercise is thought to be related to airway wall dehydration secondary to hyperventilation. More rigorous exercise protocols may have a role in detecting exercise-induced bronchoconstriction in those who otherwise have a normal response to steady-state exercise challenge.

OBJECTIVES

The objective of this study was to determine the effect of two different exercise protocols--a constant work rate protocol and a progressive ramp protocol--on pulmonary function testing in healthy adolescents. We hypothesized that vigorous exercise protocols would lead to reductions in lung function in healthy adolescents.

METHODS

A total of 56 healthy adolescents (mean age, 15.2 ± 3.3 [SD] years) were recruited to perform two exercise protocols: constant work rate exercise test to evaluate for exercise-induced bronchoconstriction (as defined by ATS) and standardized progressive ramp protocol. Pulmonary function abnormalities were defined as a decline from baseline in FEV1 of greater than 10%.

MEASUREMENTS AND MAIN RESULTS

Ten participants (17.8%) had a significant drop in FEV1. Among those with abnormal lung function after exercise, three (30%) were after the ATS test only, five (50%) were after the ramp test only, and two (20%) were after both ATS and ramp tests.

CONCLUSION

Healthy adolescents demonstrate subtle bronchoconstriction after exercise. This exercise-induced bronchoconstriction may be detected in healthy adolescents via constant work rate or the progressive ramp protocol. In a clinical setting, ramp testing warrants consideration in adolescents suspected of having exercise-induced bronchoconstriction and who have normal responses to steady-state exercise testing.

'Indirect' challenges from science to clinical practice

Indirect challenges act to provoke bronchoconstriction by causing the release of endogenous mediators and are used to identify airway hyper-responsiveness. This paper reviews the historical development of challenges, with exercise, eucapnic voluntary hyperpnoea (EVH) of dry air, wet hypertonic saline, and with dry powder mannitol, that preceded their use in clinical practice. The first challenge developed for clinical use was exercise. Physicians were keen for a standardized test to identify exercise-induced asthma (EIA) and to assess the effect of drugs such as disodium cromoglycate. EVH with dry air became a surrogate for exercise to increase ventilation to very high levels. A simple test was developed with EVH and used to identify EIA in defence force recruits and later in elite athletes. The research findings with different conditions of inspired air led to the conclusion that loss of water by evaporation from the airway surface was the stimulus to EIA. The proposal that water loss caused a transient increase in osmolarity led to the development of the hypertonic saline challenge. The wet aerosol challenge with 4.5% saline, provided a known osmotic stimulus, to which most asthmatics were sensitive. To simplify the osmotic challenge, a dry powder of mannitol was specially prepared and encapsulated. The test pack with different doses and an inhaler provided a common operating procedure that could be used at the point of care. All these challenge tests have a high specificity to identify currently active asthma. All have been used to assess the benefit of treatment with inhaled corticosteroids. Over the 50 years, the methods for testing became safer, less complex, and less expensive and all used forced expiratory volume in 1 sec to measure the response. Thus, they became practical to use routinely and were recommended in guidelines for use in clinical practice.

Assessment of allergen-induced respiratory hyperresponsiveness before the prescription of a specific immunotherapy

BACKGROUND

Asymptomatic sensitization is a frequent condition that must be considered before the indication of allergic-specific immunotherapy.

OBJECTIVE

The aim of this study was to appreciate and correlate the local and spirometric changes elicited by the allergen-specific nasal provocation test (NPT) to define practical and feasible guidelines for the allergist/immunologist to demonstrate specific respiratory hyperresponsiveness before the indication of allergic-specific immunotherapy.

METHODS

A total of 172 subjects (children and adults) with a diagnosis of allergic rhinitis were submitted to flow-volume spirometry immediately before and after the NPT performed with Dermatophagoides antigens. The differences between the pre- and postspirometric estimated values of peak expiratory flow rate (PEFdif%), forced expiratory volume in 1 second (FEV1dif%), and forced vital capacity (FVCdif%) were correlated with the results of the nasal provocation test symptom score (NPT-SS).

RESULTS

There were 119 subjects (69%) with NPT-SS > 2. Among these patients who were reactive, the mean NPT-SS was 6.3. The Spearman's correlation between PEFdif% and NPT-SS was r = -0.44 (p = 0.01); the Spearman's correlation between FEV1dif% and NPT-SS was r = -0.22 (p = 0.01), and the Spearman's correlation between FVCdif% and NPT-SS was r = -0.21 (p = 0.04).

CONCLUSION

The combined utilization of the allergen-specific NPT-SS with the spirometry (or PEF meter) is a safe methodology to evaluate allergen-specific nasal and bronchial hyperresponsiveness (which sometimes acts as a bronchial provocation test) in patients with allergic rhinitis and asthma due to hypersensitivity who are candidates for allergen-specific immunotherapy.

Asthma-associated comorbidities in children with and without secondhand smoke exposure

BACKGROUND

Secondhand smoke (SHS) exposure is known to trigger asthma, but asthma disease severity and comorbidities in children exposed to SHS are not very well quantified.

OBJECTIVE

To identify comorbidities and understand health care usage in children with asthma exposed to SHS (cases) compared with children with asthma but without SHS exposure (controls).

METHODS

A retrospective nested matched case-and-control study was conducted with children 5 to 18 years old who were enrolled in the Pediatric Asthma Management Program. Pulmonary function testing (spirometry, methacholine challenges, and exhaled nitric oxide) and body mass index were reviewed. Influenza vaccination rates, oral steroid usage, emergency department visits, and hospitalizations were assessed. Network analysis of the 2 groups also was conducted to evaluate for any associations between the variables.

RESULTS

Cases had significantly higher body mass index percentiles (>75%, odds ratio [OR] 1.64, 95% confidence interval [CI] 1.22-2.2, P = .001). Cases were less likely to have had a methacholine challenge (OR 0.49, 95% CI 0.36-0.68, P < .001) and an exhaled nitric oxide (OR 0.6, 95% CI 0.37-0.97, P = .04) performed than controls. The ratio of forced expiration volume in 1 second to forced vital capacity and forced expiration volume in 1 second were lower in cases than in controls (P < .05). Cases were less likely to have received an influenza vaccination (OR 0.61, 95% CI 0.45-0.82, P = .001) than controls. Unsupervised multivariable network analysis suggested a lack of discrete and unique subgroups between cases and controls.

CONCLUSION

Children with asthma exposed to SHS are more likely to have comorbid conditions such as obesity, more severe asthma, and less health care usage than those not exposed to SHS. Smoking cessation interventions and addressing health disparities could be crucial in this vulnerable population.

Effect of lowering methacholine challenge test cutoff in children

BACKGROUND

The diagnosis of asthma is based on clinical judgment, history of personal or familial atopy, and testing, typically with a methacholine challenge test (MCT). Guidelines suggest a provocation concentration that caused a decrease in forced expiratory volume in 1 second of 20% (PC20) cutoff of 4 mg/mL for a positive test result.

OBJECTIVE

To investigate the effect of lowering the MCT PC20 cutoff from 8 to 4 mg/mL on the number of positive test results and the distribution of test results.

METHODS

A retrospective study was conducted at the Montreal Children's Hospital from January 1, 2006, through June 31, 2012, on patients referred by nonrespiratory physicians. A 2-minute tidal breathing dosing protocol was used, and the PC20 was calculated by linear interpolation.

RESULTS

A total of 748 patients were tested using spirometry. A total of 134 (17.9%) had a negative MCT result, and 614 (81.1%) responded at 8 mg/mL or less. A total of 570 patients (92.8% of respondents) responded at a dose of 4 mg/mL or higher (median PC20 of 0.47 mg/mL), with the remainder (7.2% of respondents) responding at a dose between 4 and 8 mg/mL (median PC20 of 6.37 mg/mL). There was no difference in the number of positive test results between the sexes, regardless of cutoff. The sensitivity of MCT was 82.1% at a cutoff of 8 mg/mL and 76.2% at 4 mg/mL. With a pretest likelihood of asthma of 75%, the specificity was 71.2%.

CONCLUSION

In a standard pediatric referral population, using a PC20 cutoff of 4 mg/mL provided a sensitivity of 76.2%, and only excluded 5.8% of all those referred for suspicion of asthma (7.2% of all test results were ≤8 mg/mL). This finding suggests that a PC20 of 4 mg/mL can reasonably be used as a cutoff for a positive MCT result in children.

Airway response to exercise measured by area under the expiratory flow-volume curve in children with asthma

BACKGROUND

The exercise challenge test is the gold standard for diagnosing exercise-induced bronchoconstriction; however, it produces negative results in many children with postexercise symptoms.

OBJECTIVE

To assess the utility of the area under the expiratory flow-volume curve (Aex) to identify exercise-induced bronchoconstriction in children with asthma.

METHODS

Data from the medical records of 221 children with asthma who underwent an exercise treadmill challenge (ETC) were analyzed. The relation between exercise-induced respiratory symptoms and results of the ETC were assessed, specifically, the maximal decrease in forced expiration in 1 second (FEV1) and the maximal decrease in the Aex.

RESULTS

The receiver operating characteristic curve showed that a decrease greater than 6% in the Aex was an optimal cutoff point to produce the fewest misclassified ETC results based on a greater than 10% decrease in FEV1. The results of multivariable logistic regression showed that a decrease greater than 6% in the Aex was comparable to a decrease greater than 10% in FEV1 during an ETC and was more closely related to the presence of exercise-induced respiratory symptoms. Measuring the Aex during a routine ETC allowed a confirmation of bronchoconstriction in an additional 49 children (44%) with asthma and exercise-induced respiratory symptoms. The Aex measurement increased the sensitivity and negative predictive value of ETC without a significant effect on ETC specificity.

CONCLUSION

Measuring the Aex increases the sensitivity and negative predictive value of ETC without producing a significant change in ETC specificity. Applying a 6% decrease in the Aex as a cutoff point for a positive exercise challenge test result may prevent the underdiagnosis of exercise-induced bronchoconstriction in children with asthma and postexercise symptoms.

TRIAL REGISTRATION

This study was registered at www.clinicaltrials.gov (NCT01798823).

Evaluation of association between airway hyperresponsiveness, asthma control test, and asthma therapy assessment questionnaire in asthmatic children

Background

Achieving asthma control is a major challenge in children, otherwise symptoms perception remain poor especially at this age. The aim of this study is to evaluate the relationship between Asthma Control Test (ACT^TM), Asthma Therapy Assessment Questionnaire (ATAQ^TM) and exercise-induced bronchospasm (EIB).

Methods

We studied 80 asthmatic children. Airways hyperresponsiveness (AHR) was assessed by exercise-induced bronchospasm (Balke Protocol). Asthma control was evaluated using two questionnaires in all subjects: ACT (composed by Childhood-ACT and ACT) and ATAQ. In addition the use of short acting beta 2 agonist agents (SABAs) was assessed for each patient. Non-parametric variables were compared by Chi Square Test. Binomial logistic regression was performed to estimate the two questionnaires Odds Ratio (OR) in finding AHR.

Results

We have found that ATAQ has a sensitivity and a specificity of 0.72 and 0.45 respectively; instead, ACT has a sensitivity and a specificity of 0.5 and 0.39 respectively in evaluating AHR. Patients with uncontrolled asthma according to ATAQ revealed a significant higher percentage of AHR compared with ACT (72% vs 50%, p < 0.01).

Confirming this finding, patients declaring uncontrolled asthma to ATAQ have a significantly higher percentage (34%) of frequent SABAs use than the group with uncontrolled asthma to ACT (21%) (p <0.01).

Binomial logistic regression shows how a test revealing uncontrolled asthma is associated with the increasing odds of having AHR according to ATAQ (OR = 3.8, p = 0.05), not to ACT (OR = 0.2, p = 0.1).

Conclusions

Our results show that ATAQ reflects AHR and asthma control better than ACT. Children with uncontrolled asthma according to ATAQ have higher odds of having AHR and use of rescue medications (SABAs) compared to patients declaring uncontrolled asthma according to ACT. However both questionnaires are not sufficient alone to fully evaluate asthma control in children and it is always necessary to perform functional tests and investigate patients lifestyle, drug use and other important data that a simple questionnaire is not able to point out

Bronchial hyperresponsiveness testing in athletes of the Swiss Paralympic team

BACKGROUND

The aim of this study was to assess airway hyperresponsiveness to eucapnic voluntary hyperventilation and dry powder mannitol challenge in athletes aiming to participate at the Paralympic Games 2008 in Beijing, especially in athletes with spinal cord injury.

METHODS

Forty-four athletes with a disability (27 with paraplegia (group 1), 3 with tetraplegia (group 2) and 14 with other disabilities such as blindness or single limb amputations (group 3) performed spirometry, skin prick testing, measurement of exhaled nitric oxide, eucapnic voluntary hyperventilation challenge test (EVH) and mannitol challenge test (MCT). A fall in FEV1 of ≥10% in either challenge test was deemed positive for exercise-induced bronchoconstriction.

RESULTS

Fourteen (32%) athletes were atopic and 7 (16%) had a history of physician-diagnosed asthma. Absolute lung function values were significantly lower in patients of group 1 and 2 compared to group 3. Nine (20%) athletes were positive to EVH (8 paraplegics, 1 tetraplegic), and 8 (18%) athletes were positive to MCT (7 paraplegics, 1 tetraplegic). Fourteen (22.7%) subjects were positive to at least one challenge; only three athletes were positive to both tests. None of the athletes in group 3 had a positive test. Both challenge tests showed a significant association with physician-diagnosed asthma status (p = 0.0001). The positive and negative predictive value to diagnose physician-diagnosed asthma was 89% and 91% for EHV, and 75% and 86% for MCT, respectively.

CONCLUSION

EVH and MCT can be used to identify, but especially exclude asthma in Paralympic athletes.

Outpatient management of asthma in children

The principal aims of asthma management in childhood are to obtain symptom control that allows individuals to engage in unrestricted physical activities and to normalize lung function. These aims should be achieved using the fewest possible medications. Ensuring a correct diagnosis is the first priority. The mainstay of asthma management remains pharmacotherapy. Various treatment options are discussed. Asthma monitoring includes the regular assessment of asthma severity and asthma control, which then informs decisions regarding the stepping up or stepping down of therapy. Delivery systems and devices for inhaled therapy are discussed, as are the factors influencing adherence to prescribed treatment. The role of the pediatric health care provider is to establish a functional partnership with the child and their family in order to minimize the impact of asthma symptoms and exacerbations during childhood.

Exercise-induced bronchoconstriction: celebrating 50 years

This article examines in detail the history of more than half a century of investigations into elucidating the causation of exercise-induced bronchoconstriction. Despite earnest attempts by many researchers from many countries, answers to some pivotal questions await the next generation of investigators into exercise-induced bronchoconstriction.

Assessment of EIB: What you need to know to optimize test results

Respiratory symptoms and asthma control questionnaires are poor predictors of the presence or severity of exercise-induced bronchoconstriction (EIB), and objective measurement is recommended. To optimize the chance of a positive test result, there are several factors to consider when exercising patients for EIB, including the ventilation achieved and sustained during exercise, water content of the inspired air, and the natural variability of the response. The high rate of negative exercise test results has led to the development of surrogates to identify EIB in laboratory or office settings, including eucapnic voluntary hyperpnea of dry air and inhalation of hyperosmolar aerosols.

[Interest for evaluation of bronchial inflammation in asthma]

Asthma is a heterogeneous chronic inflammatory disease. The respiratory functional tests are sometimes insufficient to confirm the diagnosis. Other tools are developed to estimate the bronchial inflammation such as tests of bronchial provocation, measure of exhaled nitric oxide, induced sputum and exhaled breath condensate. This review presents these non-invasive methods, approaches their interests on the identification of the disease and the treatment.

Assessment of exercise-induced bronchoconstriction in adolescents and young children

Recent research shows important differences in exercise-induced bronchoconstriction (EIB) between children and adults, suggesting a different pathophysiology of EIB in children. Although exercise can trigger classic symptoms of asthma, in children symptoms can be subtle and nonspecific; parents, children, and clinicians often do not recognize EIB. With an age-adjusted protocol, an exercise challenge test can be performed in children as young as 3 years of age. However, an alternative challenge test is sometimes necessary to assess potential for EIB in children. This review summarizes age-related features of EIB and recommendations for assessing EIB in young children and adolescents.

Cough and exhaled nitric oxide levels: what happens with exercise?

Cough associated with exertion is often used as a surrogate marker of asthma. However, to date there are no studies that have objectively measured cough in association with exercise in children. Our primary aim was to examine whether children with a pre-existing cough have an increase in cough frequency during and post-exercise. We hypothesized that children with any coughing illness will have an increase in cough frequency post-exercise regardless of the presence of exercise-induced broncho-constriction (EIB) or atopy. In addition, we hypothesized that Fractional exhaled nitric oxide (FeNO) levels decreases post-exercise regardless of the presence of EIB or atopy. Children with chronic cough and a control group without cough undertook an exercise challenge, FeNO measurements and a skin prick test, and wore a 24-h voice recorder to objectively measure cough frequency. The association between recorded cough frequency, exercise, atopy, and presence of EIB was tested. We also determined if the change in FeNO post exercise related to atopy or EIB. Of the 50 children recruited (35 with cough, 15 control), 7 had EIB. Children with cough had a significant increase in cough counts (median 7.0, inter-quartile ranges, 0.5, 24.5) compared to controls (2.0, IQR 0, 5.0, p = 0.028) post-exercise. Presence of atopy or EIB did not influence cough frequency. FeNO level was significantly lower post-exercise in both groups but the change was not influenced by atopy or EIB. Cough post-exertion is likely a generic response in children with a current cough. FeNO level decreases post-exercise irrespective of the presence of atopy or EIB. A larger study is necessary confirm or refute our findings.

Physical activity and exercise-induced bronchoconstriction in Greek schoolchildren

OBJECTIVE

To investigate the association between physical activity and exercise-induced bronchoconstriction (EIB) in an urban population sample of schoolchildren, taking into account potential confounders such as asthma symptoms and overweight.

METHODS

Children aged 10-12 years answered validated questionnaires on physical activity (Physical Activity and Lifestyle Questionnaire) and asthma symptoms (ISAAC questionnaire), and were categorized according to their body mass index (BMI). EIB (FEV(1) decrease from baseline ≥13%) was assessed by a standardized free running Exercise Challenge Test (ECT).

RESULTS

Six hundred seven children completed the ECT. There were no differences among asthma groups (diagnosed asthma, asthma-related symptoms not diagnosed as asthma, no asthma-related symptoms) regarding total daily energy expenditure and time spent in mild (1.1-2.9 metabolic equivalents-METs), moderate (3-6 METs), and vigorous (>6 METs) activities. Only overweight/obese EIB-positive children had shorter duration of vigorous activity as compared to their EIB-negative or non-overweight/obese EIB-positive peers. Total daily energy expenditure and duration of mild- and moderate-intensity activity were negatively associated with EIB independently of BMI status or asthma-related symptoms.

CONCLUSIONS

Decreased levels of physical activity are associated with EIB irrespectively of BMI status and asthma-related symptoms. Longitudinal studies are needed to confirm the negative impact of sedentary lifestyle on the development of EIB suggested by these findings.

Associations and interactions of genetic polymorphisms in innate immunity genes with early viral infections and susceptibility to asthma and asthma-related phenotypes

BACKGROUND

The innate immune system is essential for host survival because of its ability to recognize invading pathogens and mount defensive responses.

OBJECTIVES

We sought to identify genetic associations of innate immunity genes with atopy and asthma and interactions with early viral infections (first 12 months of life) in a high-risk birth cohort.

METHODS

Three Canadian family-based studies and 1 Australian population-based case-control study (n = 5565) were used to investigate associations of 321 single nucleotide polymorphisms (SNPs) in 26 innate immunity genes with atopy, asthma, atopic asthma, and airway hyperresponsiveness. Interactions between innate immunity genes and early viral exposure to 3 common viruses (parainfluenza, respiratory syncytial virus, and picornavirus) were examined in the Canadian Asthma Primary Prevention Study by using both an affected-only family-based transmission disequilibrium test and case-control methods.

RESULTS

In a joint analysis of all 4 cohorts, IL-1 receptor 2 (IL1R2) and Toll-like receptor 1 (TLR1) SNPs were associated with atopy after correction for multiple comparisons. In addition, an NFKBIA SNP was associated with atopic asthma. Six SNPs (rs1519309 [TLR3], rs740044 [ILIR2], rs4543123 [TLR1], rs5741812 [LBP], rs917998 [IL18RAP], and rs3136641 [NFKBIB]) were significant (P < .05, confirmed with 30,000 permutations) in both the combined analysis of main genetic effects and SNP-virus interaction analyses in both case-control and family-based methods. The TLR1 variant (rs4543123) was associated with both multiple viruses (respiratory syncytial virus and parainfluenza virus) and multiple phenotypes.

CONCLUSION

We have identified novel susceptibility genes for asthma and related traits and interactions between these genes and early-life viral infections.

Inhaled mannitol as a test for bronchial hyper-responsiveness

Bronchial provocation tests (BPTs) are useful for identifying one of the key features of asthma: bronchial hyper-responsiveness (BHR). The symptoms of asthma are not always reflective of the underlying pathophysiology of asthma and there is a need for objective tests to identify the presence and severity of BHR. A new BPT, involving the inhalation of dry powder mannitol, has recently been approved to identify BHR and is now in use as a diagnostic tool for currently active asthma. Airway sensitivity to mannitol identifies BHR that is dependent upon the presence of airway inflammation and would probably benefit from treatment with inhaled corticosteroids. The mannitol BPT is available commercially as a (single-use) test kit (Aridol/Osmohale), with the only additional requirement to perform the test being a spirometer. Accordingly, the mannitol BPT provides a point-of-need tool to identify BHR to assist in the diagnosis of asthma.

Challenge of exercise-induced asthma and exercise-induced bronchoconstriction

Exertional dyspnea is a common clinical problem seen with different etiologies in different clinical situations and may even be found in healthy individuals. Approximately 90% of asthmatic patients suffer from shortness of breath in the context of exercise. Dyspnea, occurring during or after exercise, can be the only clinical manifestation of asthma. On the other hand, bronchoconstriction may occur in the absence of asthma - so-called exercise-induced bronchoconstriction. In elite athletes and persons performing sports with high ventilatory demand, bronchospasm in the context of exercise may appear without the presence of asthma. In these circumstances, bronchoconstriction is characterized by neutrophilic inflammation in the bronchial epithelium. Exercise-induced bronchoconstriction in the absence of asthma is difficult to diagnose and to treat. Diagnostic tests are often complex to handle, infrequently performed and the majority miss well-defined cut-off points. Diagnosis is confirmed either by performing direct or indirect bronchial challenge tests for classical asthma or through indirect tests for exercise-induced bronchoconstriction. Therapy for both diseases is based on short-acting beta-agonists used 15 min before exercise. Daily basic therapy is different for asthmatics and nonasthmatics - where basic therapy consists of inhaled corticosteroids in asthmatics, leukotriene antagonists play a more important role in exercise-induced bronchoconstriction. In general, treatment of exercise-induced asthma follows the Global Initiative of Asthma guidelines.

Asthma outcomes: pulmonary physiology

BACKGROUND

Outcomes of pulmonary physiology have a central place in asthma clinical research.

OBJECTIVE

At the request of National Institutes of Health (NIH) institutes and other federal agencies, an expert group was convened to provide recommendations on the use of pulmonary function measures as asthma outcomes that should be assessed in a standardized fashion in future asthma clinical trials and studies to allow for cross-study comparisons.

METHODS

Our subcommittee conducted a comprehensive search of PubMed to identify studies that focused on the validation of various airway response tests used in asthma clinical research. The subcommittee classified the instruments as core (to be required in future studies), supplemental (to be used according to study aims and in a standardized fashion), or emerging (requiring validation and standardization). This work was discussed at an NIH-organized workshop in March 2010 and finalized in September 2011.

RESULTS

A list of pulmonary physiology outcomes that applies to both adults and children older than 6 years was created. These outcomes were then categorized into core, supplemental, and emerging. Spirometric outcomes (FEV(1), forced vital capacity, and FEV(1)/forced vital capacity ratio) are proposed as core outcomes for study population characterization, for observational studies, and for prospective clinical trials. Bronchodilator reversibility and prebronchodilator and postbronchodilator FEV(1) also are core outcomes for study population characterization and observational studies.

CONCLUSIONS

The subcommittee considers pulmonary physiology outcomes of central importance in asthma and proposes spirometric outcomes as core outcomes for all future NIH-initiated asthma clinical research.

Evaluation of association between exercise-induced bronchoconstriction and childhood asthma control test questionnaire scores in children

OBJECTIVE

Asthma control represents a major challenge in the management of asthmatic children; however, correct perception of control is poor. The aim of the study was to evaluate the association between subjective answers given to the Childhood Asthma Control Test (C-ACT) and objective evaluation of exercise-induced bronchonstriction (EIB) by standardized treadmill exercise challenge.

METHODS

EIB was evaluated by standardized treadmill exercise challenge and related to C-ACT scores in 92 asthmatic children.

RESULTS

Of the 92 studied children only six children had a concordance between a positive challenge test (ΔFEV1 ≥ 13%) and a positive response to the exercise-related issue of the C-ACT questionnaire (C-ACT total score ≤ 19). There was no significant association between the degree of EIB and the scores relative to the single question on exercise-related problems while a significant association was found when considering the whole questionnaire with C-ACT total score > 19 (r = -0.40, P < 0.001). The two single questions showing a significant association were those focusing on nocturnal asthma. The areas under the ROC curve (AUC) for the sum of the scores of these questions in relationship to a positive response to the exercise test was 0.74. The AUC of the C-ACT total score was 0.76 and 0.55 for the specific question on EIB related problems.

CONCLUSION

The discrimination power of the C-ACT total score in relationship to EIB was moderately good, and C-ACT questionnaire was capable of correctly predicting the absence of EIB in children reporting a global score > 19. However, direct questions on EIB are associated with a high number of false positive and negative responses; better associations are found questioning on the presence on nocturnal symptoms.

Diagnostic exercise challenge testing

This article reviews the diagnostic challenge methods-both exercise and surrogate-for diagnosis of exercise-induced bronchoconstriction (EIB) and EIB with known asthma. Indirect challenges that release the entire repertoire of mediators representative of EIB and asthma are more specific for diagnosis and are recommended over direct challenges such as methacholine challenge, which are sensitive but nonspecific. Self-reported history and empiric therapeutic trials are not adequate for diagnosis of EIB with or without known asthma. Objective pulmonary function documentation with bronchodilator reversibility or exercise or surrogate challenge are optimal for diagnosis of EIB or EIB with known asthma. Such objective pulmonary function documentation is optimal for the proper management and healthy lifestyle of the exercising athlete or individual.

Relationship between exercise-induced bronchospasm (EIB) and asthma control test (ACT) in asthmatic children

OBJECTIVE

Evaluate the relationship between Asthma Control Test™ (ACT) and exercise-induced bronchospasm (EIB) in 81 asthmatic children.

METHODS

EIB was assessed in every patient by Balke protocol and asthma control was evaluated by ACT. Patients were divided into three groups: Group A (30 patients) with complete asthma control (ACT score = 25), Group B (37 patients) with partial asthma control (ACT score = 21-24), and Group C (14 patients) with poor asthma control (ACT score < 20).

RESULTS

About 36% (11/30) of patients in Group A (with complete asthma control) tested positive for EIB, whereas 21% (8/37) in Group B (with partial asthma control) and 28% (4/14) in Group C (with poor asthma control) exhibited EIB. The percentage of positive EIB was very similar between the three groups with no differences between controlled, partially controlled, and uncontrolled asthma. Statistical evaluation by χ(2)-test between complete (ACT score = 25) and not complete asthma control (ACT score < 24) confirmed a statistically significant difference (p < .01) between the obtained data.

CONCLUSIONS

It must be stated that ACT alone is not sufficient to evaluate asthma control in children correctly because it fails to detect EIB in a significant percentage of subjects.

Mannitol dry powder challenge in comparison with exercise testing in children

RATIONALE

Mannitol dry powder (MDP) challenge is an indirect bronchial provocation test, which is well studied in adults but not established for children.

OBJECTIVE

We compared feasibility, validity, and clinical significance of MDP challenge with exercise testing in children in a clinical setting.

METHODS

Children aged 6-16 years, referred to two respiratory outpatient clinics for possible asthma diagnosis, underwent standardized exercise testing followed within a week by an MDP challenge (Aridol™, Pharmaxis, Australia). Agreement between the two challenge tests using Cohen's kappa and receiving operating characteristic (ROC) curves was compared.

RESULTS

One hundred eleven children performed both challenge tests. Twelve children were excluded due to exhaustion or insufficient cooperation (11 at the exercise test, 1 at the MDP challenge), leaving 99 children (mean ± SD age 11.5 ± 2.7 years) for analysis. MDP tests were well accepted, with minor side effects and a shorter duration than exercise tests. The MDP challenge was positive in 29 children (29%), the exercise test in 21 (21%). Both tests were concordant in 83 children (84%), with moderate agreement (κ = 0.58, 95% CI 0.39-0.76). Positive and negative predictive values of the MDP challenge for exercise-induced bronchoconstriction were 68% and 89%. The overall ability of MDP challenge to separate children with or without positive exercise tests was good (area under the ROC curve 0.83).

CONCLUSIONS

MDP challenge test is feasible in children and is a suitable alternative for bronchial challenge testing in childhood.

Physical activity recommendations for children with specific chronic health conditions: Juvenile idiopathic arthritis, hemophilia, asthma and cystic fibrosis

As a group, children with a chronic disease or disability are less active than their healthy peers. There are many reasons for suboptimal physical activity, including biological, psychological and social factors. Furthermore, the lack of specific guidelines for 'safe' physical activity participation poses a barrier to increasing activity. Physical activity provides significant general health benefits and may improve disease outcomes. Each child with a chronic illness should be evaluated by an experienced physician for activity counselling and for identifing any contraindications to participation. The present statement reviews the benefits and risks of participation in sport and exercise for children with juvenile arthritis, hemophilia, asthma and cystic fibrosis. Guidelines for participation are included.

Exercise challenge test: is a 15% fall in FEV(1) sufficient for diagnosis?

INTRODUCTION

In the exercise challenge test (ECT), a drop in forced expiratory volume in the first second (FEV(1)) of between 10 and 15% is the determinant variable for a diagnosis of exercise-induced bronchospasm.

HYPOTHESIS

The use of FEV(1) plus mean forced expiratory flow between 25% and 75% of the forced vital capacity (FEF(25-75%)) may increase the sensitivity of the ECT in asthmatic children.

SPECIFIC OBJECTIVE

To compare FEV(1) and FEF(25-75%) changes in a group of asthmatic and healthy children.

METHODOLOGY

This was a cross-sectional study. Asthmatics were categorized by their severity (GINA) and after 1 month without controller therapy, an ECT was done under standard protocol. As well, a questionnaire about rhinitis and asthma was conducted with the entire population. ROC curves were used for analysis.

RESULTS

A total of 147 children (34 healthy and 113 asthmatics, 18 and 58 males, respectively) were evaluated. Divided into healthy children and intermittent, mild and moderate persistent asthmatics, they had similar average ages (9.4, 9.48, 8.97, and 11.2 years, respectively). Using a 15% fall in FEV(1), we obtained 29% sensitivity and 100% specificity. However, when we used a 10% fall in FEV(1), sensitivity was 47% and specificity was 97%. Adding a 28% fall in FEF(25-75%), sensitivity was 52% and specificity was 94%.

CONCLUSION

This study suggests that test sensitivity can increase by using a lower FEV(1) cut-off (10%) and adding a 28% fall in FEF(25-75%).

Airway hyperresponsiveness to methacholine in 7-year-old children: sensitivity and specificity for pediatric allergist-diagnosed asthma

BACKGROUND

The operating characteristics of PC(20) values used as cut-offs to define airway hyperresponsiveness, as it informs the diagnosis of asthma in children, are poorly understood. We examine data from a unique cohort to inform this concern.

OBJECTIVE

Determine the sensitivity and specificity of incremental PC(20) cut-offs for allergist-diagnosed asthma.

METHODS

Airway reactivity at age 7 was assessed in children within a birth cohort at high risk for asthma; PC(20) for methacholine was determined by standard technique including interpolation. The diagnosis of asthma was considered by the pediatric allergist without knowledge of the methacholine challenge results. Sensitivity and specificity were calculated using a cross-tabulation of asthma diagnosis with incremental PC(20) cut-off values, from 1.0 to 8.0 mg/ml, and plotted as receiver operator characteristic (ROC) curves. The "optimal" cut-off was defined as that PC(20) conferring maximal value for sensitivity plus specificity while the "balanced" cut-off was defined as that PC(20) at which sensitivity and specificity were most equal.

RESULTS

70/348 children (20.1%) were diagnosed with asthma. The optimal and balanced PC(20) cut-offs, both for all children and for females alone, were respectively 3 mg/ml (sensitivity 80.0%, specificity 49.1%) and 2 mg/ml (sensitivity 63.1%, specificity 64.7%). For males alone, the "optimal" and "balanced" PC(20) cut-offs were both 2 mg/ml.

CONCLUSION

For this cohort of 7-year olds at high risk for asthma, methacholine challenge testing using a cut-off value of PC(20) 3 mg/ml conferred the maximal sum of specificity plus sensitivity. For contexts in which higher sensitivity or specificity is desired, other cut-offs may be preferred.

Airway response to exercise by forced oscillations in asthmatic children

Forced expiratory volume in 1 s (FEV1) detection of exercise-induced bronchoconstriction (EIB) to identify asthma has good specificity but rather low sensitivity. The aim was to test whether sensitivity may be improved by measuring respiratory resistance (Rrs) by the forced oscillation technique (FOT). Forty-seven asthmatic and 50 control children (5-12 y) were studied before and after running 6 min on a treadmill. Rrs in inspiration (Rrsi) and expiration (Rrse), FEV1 and Rrsi response to a deep inhalation (DI) were measured before and after exercise. In asthmatics versus controls, exercise induced significantly larger increases in Rrsi (p < 0.001) and larger decreases in FEV1 (p = 0.004). Asthmatics but not controls showed more bronchodilation by DI after exercise (p = 0.02). At specificity >0.90, sensitivity was 0.53 with 25% increase Rrsi and 0.45 with 27% increase Rrse or 5% decrease FEV1. It is concluded that the FOT improves sensitivity of exercise challenge, and the Rrsi response to DI may prove useful in identifying the mechanism of airway obstruction.

The reciprocal influences of asthma and obesity on lung function testing, AHR, and airway inflammation in prepubertal children

Although asthma and obesity are among the major chronic disorders their reciprocal or independent influences on lung function testing, airways hyperresponsiveness (AHR) and bronchial inflammation has not been completely elucidated. In 118 pre-pubertal Caucasian children anthropometric measurements functional respiratory parameters (flow/volume curves at baseline and after 6-minute walk test [6MWT]) together with bronchial inflammatory index (FeNO) were assessed. The study population was divided into four groups according to BMI and the presence or absence of asthma: Obese asthmatic (ObA) Normal-weight asthmatic (NwA), Obese non-asthmatic (Ob), non-asthmatic normal-weight children (Nw). Baseline PEF and MEF(75) (%-expected) were significantly different across the four groups with significantly lower values of MEF(75) in ObA and Ob children when compared to Nw children (P = 0.004 and P = .0001, respectively) and this independent role of obesity on upper respiratory flows was confirmed by multiple analysis of covariance. After 6 MWT respiratory parameters decreased only in ObA and NwA children and 12 children presented a positive fall in FEV(1), in contrast no changes of respiratory function testing were detected in Ob and Nw children, and only 2 Ob children presented a significant fall in FEV(1). FeNO analysis demonstrated significantly higher values in ObA and NwA children when compared to Ob (P = 0.008 and P = 0.0002, respectively) and Nw children (P = 0.0001 and P = 0.0003, respectively), although a significant difference was found between Ob and Nw children (P = 0.0004). Multiple analysis of covariance confirmed an independent role of asthma on this parameter. In conclusion while AHR and airway inflammation are clearly associated with an asthmatic status, obesity seems to induce reduction of upper airways flows associated with a certain degree of pro-inflammatory changes.

Indirect challenge tests: Airway hyperresponsiveness in asthma: its measurement and clinical significance

Indirect challenges cause the release of endogenous mediators that cause the airway smooth muscle to contract and the airways to narrow. Airway sensitivity to indirect challenges is reduced or even totally inhibited by treatment with inhaled corticosteroids (ICS), so a positive response to an indirect stimulus is believed to reflect active airway inflammation. The indirect challenges commonly used in pulmonary function laboratories include exercise, eucapnic voluntary hyperpnea, hypertonic (4.5%) saline, and mannitol. Exercise was the first test to be standardized and was used to identify exercise-induced bronchoconstriction (EIB). The inhibition of EIB in young children by sodium cromoglycate led to the concept that mast cells were important very early in the onset of asthma. All of these indirect challenges are associated with the release of mast cell mediators (eg, prostaglandins, leukotrienes, and histamine). The hypertonic saline and mannitol challenges arose from the concept that EIB was caused by an increased osmolarity of the airway surface with release of mediators. These osmotic aerosols simplified testing with indirect challenges in the laboratory, improving the potential to identify currently active asthma. Although hyperresponsiveness to indirect challenges is frequently associated with a sputum eosinophilia, it is not a prerequisite because the mast cell is the most important source of mediators. The mechanism for ICS reducing hyperresponsiveness to indirect challenges likely involves both mast cells and eosinophils. Indirect challenges are appropriate to inform further on both the pathogenesis of asthma and the role of antiinflammatory agents in its treatment.

Reproducibility of the airway response to an exercise protocol standardized for intensity, duration, and inspired air conditions, in subjects with symptoms suggestive of asthma

BACKGROUND

Exercise testing to aid diagnosis of exercise-induced bronchoconstriction (EIB) is commonly performed. Reproducibility of the airway response to a standardized exercise protocol has not been reported in subjects being evaluated with mild symptoms suggestive of asthma but without a definite diagnosis. This study examined reproducibility of % fall in FEV1 and area under the FEV1 time curve for 30 minutes in response to two exercise tests performed with the same intensity and duration of exercise, and inspired air conditions.

METHODS

Subjects with mild symptoms of asthma exercised twice within approximately 4 days by running for 8 minutes on a motorized treadmill breathing dry air at an intensity to induce a heart rate between 80-90% predicted maximum; reproducibility of the airway response was expressed as the 95% probability interval.

RESULTS

Of 373 subjects challenged twice 161 were positive (≥ 10% fall FEV1 on at least one challenge). The EIB was mild and 77% of subjects had <15% fall on both challenges. Agreement between results was 76.1% with 56.8% (212) negative (< 10% fall FEV1) and 19.3% (72) positive on both challenges. The remaining 23.9% of subjects had only one positive test. The 95% probability interval for reproducibility of the % fall in FEV1 and AUC0-30 min was ± 9.7% and ± 251% for all 278 adults and ± 13.4% and ± 279% for all 95 children. The 95% probability interval for reproducibility of % fall in FEV1 and AUC0-30 min for the 72 subjects with two tests ≥ 10% fall FEV1 was ± 14.6% and ± 373% and for the 34 subjects with two tests ≥ 15% fall FEV1 it was ± 12.2% and ± 411%. Heart rate and estimated ventilation achieved were not significantly different either on the two test days or when one test result was positive and one was negative.

CONCLUSIONS

Under standardized, well controlled conditions for exercise challenge, the majority of subjects with mild symptoms of asthma demonstrated agreement in test results. Performing two tests may need to be considered when using exercise to exclude or diagnose EIB, when prescribing prophylactic treatment to prevent EIB and when designing protocols for clinical trials.